To heavily sync with the music rhythm, I found it helps to listen and place a marker, m key, at the points you want and still change. Then you can use a tool like Vasst Fasst app StillMotion to automatically place events at marker and size them to the space between the markers.
I did a slideshow mountain bike video to Guns N' Roses November rain. I was doing it the hard way until I found out about StillMotion. It is still a ridiculous amount of work since I had custom zooms on each clip.
StillMotion is just a Vegas script extension. Any limitations come down to Vegas itself. I have laid down a touch over 100 stills at once with StillMotion.
Even if there were a limit of say 100, then that still beats positioning and sizing 100 stills manually versus automatically. You don't have to drop the whole video length at once. You can break it into sections. Once stills are placed you no longer need the markers.
I would imagine that the hard part was gathering all of the images and deciding which to use. As mentioned, tools like VASST StillMotion and Ultimate S Pro make laying down the images to the music rather easy using markers and tapping to the beat.
I couldn't help but notice that from the dawn of time to the mid point of the video it was already World War II so 1/2 of the video was about the later part of the 20th century but I like the concept.
In my case it was over 1800 pix. I used Vegas 12 and did it all by hand. I was working with an old song and trying to get the clips (usually) to fly by on every 8th note. This only gave a few frames per clip, and the song tempo did not sync exactly with a 30 frame per second "rhythm". I would have to manually make some clips longer and then some shorter to keep it somewhere in the "groove".
I certainly did not work on it straight through, but it took maybe three weeks at a couple hours (or more) a day. Part of that is because I tried to match clips with the last word of each phrase, etc.
(Actually, I should say it took at least a few weeks to find the clips. The three weeks was then used to pick and assemble the pictures).
I wouldn't say it's amazing. I would say it's OK. I saw a few mistakes when the image didn't have the same aspect ratio. The speed of the images and the transitions didn't do a great job at conveying the information or tell the story. it was just a bit too fast, and trying to express the story of mankind with batman music just doesn't sit right with me. I'm just being a snob though. Obviously someone put a lot of work into it, and it's not bad, but I just don't think it's amazing.
What's mainly missing is a graphics component for continuity. It's irritating to throw just one picture after another without giving any thought to what happens between pictures. There's a right fit and a wrong fit and that takes skill and time to find. One needs to be sensitive to what happens when one image becomes the next one to give the story fluidity that doesn't irritate but amazes. It's called art direction and that's what's missing here.
Its clever. But it strobes a lot. Found it hard to watch. Sorry, don't mean to be harsh. I see a lot of effort has gone into it but didn't have time to take in those very powerful images. Somehow the potential energy of this piece got lost for me because of that. Hope this comment is useful and taken as constructive :)
What might have been cool would be to have something to focus on in the foreground while the pictures went buy in the background, maybe somewhat grayed out or faded. Then the speed of them wouldn't be a problem either.